Lecture 4: Boolean Expressions and Conditionals

Vocabulary flashcards covering procedural knowledge, boolean expressions, relational and Boolean operators, and Python conditionals (if, elif, else) including indentation and common patterns.

Boolean Expressions

Expressions that evaluate to True or False and are used to control program flow in conditionals.

Relational Operators

Operators that compare two values to produce a Boolean result (e.g., \text{==}, \text{!=}, \text{

Equality (==)

Operator that checks if two values are equal; note that \text{=} is used for assignment.

Assignment (=)

Operator that assigns a value to a variable.

Inequality (!=)

Operator that tests whether two values are not equal.

Less Than (<)

Operator that tests whether one value is smaller than another.

Greater Than (>)

Operator that tests whether one value is larger than another.

Less Than or Equal (<=)

Operator that tests whether a value is less than or equal to another.

Greater Than or Equal (>=)

Operator that tests whether a value is greater than or equal to another.

Boolean Operators

Operators that combine Boolean values: \text{and}, \text{or} , \text{not}.

and

True only if both operands are True; otherwise False.

or

True if at least one operand is True; otherwise False.

not

Logical negation that inverts a Boolean value.

Order of Operations (Boolean Expressions)

Rules for evaluating expressions: \text{not} before \text{and} before \text{or}; relational operators before Boolean operators; use parentheses for clarity.

Parentheses

Used to group parts of an expression to enforce order of evaluation.

Boolean Literals

The literals \text{True} and \text{False} used as Boolean values in conditions.

Between 0 and 100 Inclusive

A common range check example: \text{(variable >= 0) and (variable <= 100)}.

Conditional

A programming construct that selects a branch of code to execute based on a boolean condition.

Sequential

A programming construct where statements are executed one after another in order.

Indentation

In Python, indentation defines blocks of code; four spaces per level is common and required for blocks.

The if Statement

A conditional that introduces a branch; format: \text{if :} followed by an indented block.

The if-else Statement

Conditional with two branches: execute the first block if condition is True; otherwise execute the \text{else} block.

The if-elif-else Statement

Multiple conditional branches; the first True condition's block is executed; others are skipped until \text{else}.

Nested Branches

An \text{if/elif/else} statement inside another conditional block to reflect complex logic; requires consistent indentation.

First True Expression Wins

In an \text{if-elif-else} chain, the first condition that evaluates to True is executed and later conditions are ignored.